In machining components handled in various kinds of industrial fields such as automobiles, machinery, precision equipment, electrics, electronics, and optics, (i) oil-based machining oils with a mineral oil or the like as a main component, (ii) water-soluble machining oils emulsified in water by adding a surfactant to a mineral oil or the like, (iii) fine particles, or the like are used. Among them, water-soluble machining oils are widely used mainly in cutting, grinding, or the like. For components manufactured through multiple machining processes, different machining oils may be used for the processes, and the machining oils, fine particles, and machining scrap adhere to the surface of the machined components in a mixed manner, whereby various kinds of organic and inorganic contaminants often adhere thereto in a complex manner. Various kinds of organic and inorganic contaminants such as grease, plastic, machine oil, coal tar, clay, sand, and lipid also adhere to piping and apparatuses of various kinds of factories such as oil refinery plants and chemical plants, components obtained by disassembling automobiles, industrial machines, or the like, and metal products, resin products, and textile products used in everyday life, or the like in a complex manner.
When cleaning articles to which such various kinds of organic and inorganic contaminants adhere in a complex manner, cleaners used include chlorine-based solvents such as trichloroethylene and methylene chloride, aqueous cleaners, semi-aqueous cleaners obtained by compounding water-soluble solvents with aqueous cleaners, hydrocarbon-based detergents, alcohol-based cleaners such as isopropanol (2-propanol), and glycol ether-based cleaners. However, none of them can satisfy all requirements such as cleaning ability, dryness, safety, economy, and toxicity for components to which various kinds of organic and inorganic contaminants adhere in a complex manner.
To clean articles to which various kinds of organic and inorganic contaminants adhere, a cleaner composition is developed that contains a nonaqueous cleaner such as a hydrocarbon-based cleaner, a surfactant, a polar solvent, and water in predetermined proportions and forms a W/O microemulsion or a solubilized W/O emulsion (refer to Patent Literature 1, for example). However, in the cleaner composition of Patent Literature 1, the polar solvent is used for the formation of the microemulsion, and the cleaner composition cannot be used for cleaning plastic or rubber materials that have low tolerance against polar solvents, and the plastic or rubber materials that have low tolerance against polar solvents cannot be used as cleaning tools. In addition, there is another problem in that the polar solvent is accumulated in a nonaqueous detergent used in a replacement process as a post-process of a cleaning process, and it is difficult to sustain constant cleaning ability.
A neutral aqueous liquid cleaner composition for liquid crystal panel terminal use is disclosed that contains an alkyl ether of a fatty acid alkylene oxide adduct, a glycol ether-based compound, a C8-18 aliphatic hydrocarbon, and a dialkyl sulfosuccinate (refer to Patent Literature 2, for example). However, the cleaner composition of Patent Literature 2 also contains the glycol ether-based compound as a polar solvent for the sake of liquid stability, and the cleaner composition cannot be used for cleaning the plastic or rubber materials that have low tolerance against polar solvents, and the plastic or rubber materials that have low tolerance against polar solvents cannot be used as cleaning tools. In addition, water is used in a replacement process as a post-process of a cleaning process, and the cleaner composition is hard to dry and is inferior in economy.
Furthermore, a method of cleaning is developed that uses a microemulsion type cleaner composition containing an organic solvent selected from aliphatic hydrocarbons, alkylene glycol monoethers, and dialkylene glycol monoethers, water, and a surfactant (refer to Patent Literature 3, for example). However, the cleaner composition of Patent Literature 3 contains a large amount of water, which is 30 parts by weight to 70 parts by weight, especially 35 parts by weight to 60 parts by weight, and detergency against organic contaminants is insufficient, and in addition, a process to remove water adhering to the surface is required before a replacement process with an organic solvent or the like after cleaning with the cleaner composition, thus requiring time for the cleaning process.
Furthermore, a W/O emulsion type hydrocarbon-based cleaner is developed that contains a monocarboxylic acid, a monoalkyl amine, a hydrocarbon, a nonionic surfactant, and water (refer to Patent Literature 4, for example). To reuse a cleaner liquid, the clearing liquid after cleaning treatment is required to be subjected to phase separation to extract a water phase, which is inefficient.
Meanwhile, a hydrocarbon-based cleaner containing a saturated hydrocarbon compound and glycol ethers and a method of cleaning thereof are developed (refer to Patent Literature 5, for example). It is described that the hydrocarbon-based cleaner of Patent Literature 5 has a volume resistivity of 1×108 Ω·cm or more and 1×1013 Ω·cm or less and is resistant to electrification, and even when a chargeable object to be cleaned is cleaned, no electrification occurs on the object to be cleaned, and it can be used safely. However, the volume resistivity is not exactly sufficiently low, and electrification may occur, and in addition, a polar solvent such as glycol ether is used, and the hydrocarbon-based cleaner cannot be used for cleaning the plastic or rubber materials that have low tolerance against polar solvents, and the plastic or rubber materials that have low tolerance against polar solvents cannot be used as cleaning tools.